During the production of titanium stabilized stainless steel, as titanium in steel has a tendency to reacting with SiO2 in mould fluxes to generate TiO2 into mould fluxes and mould powder can inevitably pick up Ti-bearing inclusions floating up from steel, TiO2 content in the molten mould fluxes gradually increases so that physiochemical properties of the fluxes change. To evaluate the effect of TiO2 increase in mould fluxes on the structure of the mould flux, the glassy slag system CaO–SiO2–CaF2–TiO2 for stainless steel casting fluxes was studied by combining Raman spectroscopy with 29Si and 19F Magic Angular spinning Nuclear Magnetic resonance (MAS-NMR) to obtain the structure information. Both Raman and 29Si MAS-NMR investigation results have shown that Q2 is predominant silicate species in structures of all samples. Ti4+ mainly exists in the form of [TiO4] in slag, and forms TiO2-like clusters with Ti4+ in tetrahedral coordination, which cannot change the degree of polymerization of the silicate network. A small amount of Ti enters into the silicate network as the role of network formation, which slightly enhances the degree of polymerization of the silicate network. According to 19F MAS-NMR spectra, most of the fluorine is exclusively coordinated by Ca2+ corresponding to F–Ca(n) site and only a few Si–F bonds were observed in samples. Increase of TiO2 content has no significant effects on the F- bonds.
